1. Field of the Invention
The present invention relates to an apparatus for diagnosing a fuel vapor purge system for an internal combustion engine of a vehicle. The apparatus diagnoses and detects leakage of the system.
2. Description of Related Art
JP-A-05-125997 discloses an apparatus for detecting leakage of a fuel vapor purge system. In this apparatus, a remaining amount of fuel in a tank is taken into consideration of a detection of leakage, because a pressure change in the tank is influenced by a capacity of air in the tank indicated by the remaining amount of fuel in the tank.
However, the pressure in the tank is also changed according to an evaporated amount of fuel after the purge system is hermetically closed.